Wide dynamic range continuous wave (CW) Doppler receiver

Abstract

A Doppler receiver has a wide dynamic range and operates in a differential mode. In one embodiment, the invention is a wide dynamic range continuous wave (CW) Doppler receiver, comprising a differential fixed frequency output mixer configured to receive a radio frequency (RF) input signal and supply a differential signal output; a differential fixed frequency bandpass filter coupled to the differential fixed frequency output mixer and configured to provide a fixed frequency output; an in-phase mixer and a quadrature-phase mixer, each configured to receive a differential signal output of the differential fixed frequency bandpass filter; at least one in-phase filter configured to receive the output of the in-phase mixer and supply a filtered in-phase signal; at least one quadrature-phase filter configured to receive the output of the quadrature-phase mixer and supply a filtered quadrature-phase signal; and an analog-to-digital converter configured to receive the filtered in-phase signal and the filtered quadrature-phase signal and supply a corresponding in-phase digital output and a corresponding quadrature-phase digital output, the outputs of the analog-to-digital converter supplied to a memory element.

What is claimed is:  
     
       1. A wide dynamic range continuous wave (CW) Doppler receiver that operates in a fully differential mode, comprising: 
       a differential fixed frequency output mixer configured to receive a radio frequency (RF) input signal and supply a differential signal output;  
       a differential fixed frequency bandpass filter coupled to the differential fixed frequency output mixer and configured to provide a differential fixed frequency output;  
       an in-phase mixer and a quadrature-phase mixer, each configured to receive a differential signal output of the differential fixed frequency bandpass filter;  
       at least one in-phase differential low-pass filter configured to receive the output of the in-phase mixer and supply a filtered in-phase signal;  
       at least one quadrature-phase differential low-pass filter configured to receive the output of the quadrature-phase mixer and supply a filtered quadrature-phase signal;  
       an in-phase and quadrature-phase fixed differential high-pass clutter filter; and  
       an analog-to-digital converter configured to receive the filtered in-phase signal and the filtered quadrature-phase signal and supply a corresponding in-phase digital output and a corresponding quadrature-phase digital output, the outputs of the analog-to-digital converter supplied to a memory element.  
     
     
       2. The Doppler receiver of  claim 1 , wherein the analog-to-digital converter is a high precision, 24 bit 100 kilosample per second analog-to-digital converter. 
     
     
       3. The Doppler receiver of  claim 1 , wherein the differential fixed frequency bandpass filter, the in-phase mixer, the quadrature-phase mixer, the at least one in-phase differential low-pass filter, the at least one quadrature-phase differential low-pass filter, the high-pass clutter filters, and the analog-to-digital converter operate in a differential mode. 
     
     
       4. The Doppler receiver of  claim 1 , wherein the fixed frequency output mixer provides an output at a frequency of 1 megahertz (MHz). 
     
     
       5. The Doppler receiver of  claim 1 , further comprising: 
       a second filter configured to receive the output of the in-phase mixer; and  
       a second filter configured to receive the output of the quadrature-phase mixer.  
     
     
       6. The Doppler receiver of  claim 1 , wherein the frequency of the filtered in-phase signal and the frequency of the filtered quadrature-phase signal correspond to movement of fluid or tissue represented by the radio frequency (RF) input signal. 
     
     
       7. The Doppler receiver of  claim 1 , wherein a sign of the phase difference of the filtered in-phase signal and the filtered quadrature-phase signal correspond to a direction of the movement of fluid or tissue represented by the radio frequency (RF) input signal. 
     
     
       8. The Doppler receiver of  claim 1 , wherein the in-phase mixer and the quadrature-phase mixer receive an 1 MHz local oscillator signal and supply a baseband output signal. 
     
     
       9. The Doppler receiver of  claim 8 , wherein the in-phase mixer and the quadrature-phase mixer supply a baseband signal the frequency of which represents blood flow or tissue movement represented by the radio frequency (RF) input signal. 
     
     
       10. A method for operating a wide dynamic range continuous wave (CW) Doppler receiver in a fully differential mode, comprising: 
       providing a radio frequency (RF) input signal to a differential fixed frequency output mixer, the differential fixed frequency output mixer configured to supply a differential signal output;  
       coupling a differential fixed frequency bandpass filter to the differential fixed frequency output mixer, the differential fixed frequency bandpass filter configured to provide a fixed frequency output;  
       providing a differential signal output of the differential fixed frequency bandpass filter to an in-phase mixer and a quadrature-phase mixer;  
       providing an output of the in-phase differential mixer to at least one in-phase differential low-pass filter, the in-phase differential low-pass filter configured to supply a filtered in-phase signal;  
       providing an output of the quadrature-phase differential mixer to at least one quadrature-phase differential low-pass filter, the quadrature-phase differential low-pass filter configured to supply a filtered quadrature-phase signal;  
       providing the filtered in-phase signal and the filtered quadrature-phase signal to a fixed differential high-pass clutter filter and  
       coupling an analog-to-digital converter to the output of the in-phase high-pass clutter filter and the quadrature-phase high-pass clutter filter, the analog-to-digital converter configured to supply a corresponding in-phase digital output and a corresponding quadrature-phase digital output, the outputs of the analog-to-digital converter supplied to a memory element.  
     
     
       11. The method of  claim 10 , wherein the analog-to-digital converter is a high precision, 24 bit 100 kilosample per second analog-to-digital converter. 
     
     
       12. The method of  claim 10 , further comprising operating the differential fixed frequency bandpass filter, the in-phase mixer, the quadrature-phase mixer, the at least one in-phase differential low-pass filter, the at least one quadrature-phase differential low-pass filter, the fixed differential high-pass clutter filters, and the analog-to-digital converter in a differential mode. 
     
     
       13. The method of  claim 10 , wherein the differential fixed frequency output mixer provides an output at a frequency of 1 megahertz (MHz). 
     
     
       14. The method of  claim 10 , wherein the frequency of the filtered in-phase signal and the frequency of the filtered quadrature-phase signal correspond to movement of fluid or tissue represented by the radio frequency (RF) input signal. 
     
     
       15. The method of  claim 10 , wherein a sign of the phase difference of the filtered in-phase signal and the filtered quadrature-phase signal correspond to a direction of the movement of fluid or tissue represented by the radio frequency (RF) input signal. 
     
     
       16. The method of  claim 10 , wherein the in-phase mixer and the quadrature-phase mixer receive an 1 MHz local oscillator signal and supply a baseband output signal. 
     
     
       17. The method of  claim 16 , wherein the in-phase mixer and the quadrature-phase mixer supply a baseband signal whose frequency represents blood flow or tissue movement represented by the radio frequency (RF) input signal.